1. As for the 80cc, in fact there is no such cc bicycle engine in china market, we called our 47*38(bore*stroke) engine F80 before ,but now we correct it, because its displacement is only 66cc(from EPA test report).

2. How to caculate the engine capacity. The fomula is listed below.

The volume of a cylinder=(bore area)x stroke

Bore area= Bore x Bore x pi / 4. (pi has a value of 3.14159)

Take our ZM70-P for example, its bore is 4.7cm(47mm), its stroke 3.8cm(38mm)